Multifunctional Conductive Fiber Based On Liquid Metal/Self-healing Polymer

As an important part of wearable electronic products and smart textiles,conductive fiber has attracted extensive attention.However,during the use of conductive fiber,it is inevitable that the conductive path will be destroyed or the polymer matrix will crack or damage due to external forces.These problems will cause the attenuation or loss of electrical and mechanical properties of conductive fiber and shorten its service life.Preparation of stretchable conductive fiber with self-healing ability is an effective way to solve these problems.However,there are still few reports about self-healing conductive fiber,and some problems need to be solved.On the one hand,self-healing can only be realized under specific external stimulus conditions(such as light and heat).On the other hand,when conventional metal nanomaterials or carbon materials are used as conductive fillers,the mechanical mismatch between the solid conductive component and the flexible polymer matrix is easy to occur,which affects the use of fibers.More importantly,there are no reports of stretchable conductive fibers that can self-healing structure and function in complex environments such as underwater and low temperature.In this paper,a self-healing stretchable conductive fiber was prepared by combining self-healing polymer with liquid metal through special structural design.The mechanical and electrical properties of the fibers enable efficient self-healing in a variety of complex operating environments,including room temperature,underwater and-18 °C,without any external stimulation.In this paper,the healing mechanism of self-healing conductive fiber is analyzed,and its mechanical properties,electrical properties and self-healing properties are systematically studied.By applying it to the fields of self-healing signal transmission line and wearable self-healing sensor,its broad application prospect is proved.The main research contents and results of this paper are as follows:(1)Based on reasonable molecular structure design,a self-healing polymer(SHP)based on dynamic imine and disulfide bond was synthesized.SHP can achieve high healing efficiency in a variety of complex conditions without consuming any external energy.Completely severed SHP was healed at room temperature for 8 h,the healing efficiency of stress and strain was 92% and 99%respectively.After 24 h underwater healing,the healing efficiency of stress and strain is 92% and 94% respectively.At-18 °C for 24 h,the healing efficiency of stress and strain was 87% and 88% respectively.At-50 °C for 24 h,the healing efficiency of stress and strain was 72% and 86% respectively.(2)A LM-based stretchable self-healing conductive fiber(C-SHF)was prepared by combining SHP with self-healing liquid metal(LM)through a unique sacrificial template assisted coaxial spinning(STACS)method and a simple coating method.C-SHF can self-healing electrical conductivity and mechanical properties in a variety of complex operating environments without any external stimuli.Thanks to its excellent self-healing properties,C-SHF can be self-woven.In addition,C-SHF has good resistance stability,and its resistance remains relatively stable even after continuous tensile strain reaches 180% or 1000 cycles at 50%tensile strain.(3)C-SHF can be used as a self-healing signal transmission line due to its excellent tensile properties,resistance stability and self-healing properties.The C-SHF before and after healing can stably transmit square wave signals,audio signals and video signals under large strain or under different operating conditions.C-SHF can maintain signal-to-noise ratio(SNR)and total harmonic distortion(THD)comparable to commercial cables before and after healing and under stretch condition.(4)As application extension,C-SHF was further treated.A fiber type self-healing capacitance sensor(SHS)was obtained by coating a layer of LM on the C-SHF surface,and then encapsulation with SHP.Thanks to the self-healing performance of SHP and LM,SHS has excellent self-healing ability.SHS had obvious response to external pressure stimulation before and after healing.The SHS also acts as a human motion detector that can recognize and distinguish small changes in movement,such as finger bending,smiling,cheek bulging,swallowing and coughing.In addition,SHS was integrated into the gripper to simulate the grasping process of the robot’s claw,and the application of the sensor in the field of flexible robot was studied.